1. Field of the Invention
This invention relates to a rear suspension system for a vehicle, and more particularly to a mounting structure for mounting a rear suspension system in conjunction with a differential.
2. Description of the Prior Art
Vehicles having a trailing arm type suspension system are generally provided with a suspension mounting frame which extends in the transverse direction of the vehicle body and is supported by the vehicle body at both ends thereof. The trailing arms for supporting the rear wheels are pivoted on the suspension mounting frame. In the case in which the vehicle having such suspension system is of front-engine rear-drive type, the differential is generally disposed at the rear of the suspension mounting frame. As is disclosed in Japanese Unexamined Utility Model Publication No. 57(1982)-90211, there has been known a rear suspension system for a vehicle having a differential at the rear of a suspension mounting frame in which the differential case is supported by the vehicle body at a rear portion thereof and is fixedly connected to an intermediate portion of the suspension mounting frame at a front portion thereof.
However, the conventional rear suspension system has a drawback that vibration of the differential is transmitted to the suspension mounting frame and the trailing arms to adversely affect the suspension system and is further transmitted to the vehicle body by way of the suspension mounting frame since the front portion of the differential case is fixedly connected to the intermediate portion of the suspension mounting frame even if both ends of the suspension mounting frame and the rear portion of the differential case are connected to the vehicle body by way of resilient material bodies.
The vibration of the differential could be prevented from being transmitted to the suspension mounting frame by connecting the front portion of the differential case to the intermediate portion of the suspension mounting frame by way of a resilient material body. However, when the front portion of the differential case and the intermediate portion of the suspension mounting frame are connected to each other by way of a resilient material body, restraint on the position of the intermediate portion of the suspension mounting frame is weakened to permit displacement of the intermediate portion of the suspension mounting frame to some extent. This can produce, together with various causes such as vibration of the differential, pitching of the suspension mounting frame (torsional movement about a horizontal axis passing through the connections of the suspension mounting frame to the vehicle body) which is transmitted to the trailing arms to unsettle the suspension system, thereby lowering the running stability of the vehicle.
Further, it is proposed in Japanese Patent Publication No. 58(1983)-24290 to support the front portion of the differential case by way of a resilient material body on a cross member provided to extend in the transverse direction of the vehicle body separately from the suspension mounting frame. However, in the case of a passenger car having a monocoque body, for instance, it is difficult and undesirable to provide a cross member exclusively for supporting the differential on the underside of the floor.